2. Next, roll and flatten the brown clay in the same way, and then stack the two pieces of clay on top of each other.
3. Pinch the green clay into several leaf shapes, then use a knife to cut out the veins of the leaves.
4: Pinch strawberries out of red clay and fill them with white strawberry seeds before placing them on top of the cake.
5. Use chocolate-colored clay to form a triangle of chocolate, and draw lines on it to make a simple cake.
Clay, is an important mineral raw material. It is a very small (<2?m) plasticized aluminum silicate salt. In addition to aluminum, clay contains small amounts of magnesium, iron, sodium, potassium, and calcium, and is generally formed by the weathering of silicate minerals on the earth's surface.
Clay is an important mineral raw material, widely distributed in rocks and soils all over the world, and is used in the manufacture of ceramic products, refractory materials, building materials and so on.
Clay, often misspelled as clay, is a plastic aluminum silicate salt with very small (<2?m) particles. In addition to aluminum, clays contain small amounts of magnesium, iron, sodium, potassium, and calcium. Clays are generally formed by weathering of silicate minerals on the earth's surface. But some rock-forming processes also produce clays. The presence of clays during these processes can serve as an indicator of the progress of diagenesis.
Clay is an important mineral raw material. It consists of a variety of hydrated silicates and a certain amount of alumina, alkali metal oxides and alkaline earth metal oxides, and contains quartz, feldspar, mica and impurities such as sulfates, sulfides and carbonates.
Clay minerals are fine grained, often within colloidal dimensions, crystalline or amorphous, mostly flaky, a few tubular and rod-like.
Clay minerals have plasticity when wetted with water, and can be deformed and kept in their original state for a long time under a small pressure, and have a large specific surface area, with a negative electrical charge on the particles, so they have good physical adsorption and surface chemical activity, and have the ability to exchange with other cations.
The chemical composition of clay, mineral composition and particle composition determines the process performance of clay:
Plasticity
Clay mixed with the right amount of water to form a mud mass, under the action of external forces, the mud mass deformation but not cracking, after the external forces are dispersed, but still maintain the original shape unchanged, the nature of the clay is called plasticity.
Combination
The combination of clay refers to the ability of clay to combine non-plastic raw materials to form a good plastic mud and have a certain dry strength. Clay binding has an important effect on the drying, trimming and glazing of semi-finished pieces. Clay scale bonding by its combination of barren material bonding force of the size of the decision, and the size of the bonding force and the type of clay minerals, structure and other factors related to the clay. Generally speaking, the plasticity of the clay, its binding force is also large.
Thixotropy
When clay slurry or plastic clay mass is vibrated or stirred, the viscosity will be reduced, while its fluidity will be increased, and it will gradually return to its original state after resting. In addition, after a period of time, the slurry will also thicken and solidify under the condition that the original moisture remains unchanged. This property of clay is called thixotropy.
Shrinkage
Clay mud at a certain temperature when drying, due to the discharge of water between the particles, the particles close to each other as well as the shortening of the spacing between the particles caused by the volume of contraction, known as drying shrinkage. After drying clay mud after high-temperature calcination, due to the occurrence of such as dehydration, decomposition, the generation of mullite, quartz crystal transformation, fusible impurity transformation, and various types of molten material to fill the interstitial space between the texture of a series of physicochemical changes, making the clay mud further contraction, known as sintering contraction. The total change in size of a molded clay sample after drying and calcining is called total shrinkage.
Sintering
Clay is a mixture of many minerals and does not have a fixed melting point, but softens gradually over a range of temperatures.
When the clay in the process of heating and calcination, reach a certain temperature (800 ℃ ~ 900 ℃), continue to increase the temperature, the clay in the low **** melting material began to melt, the liquid phase appeared and gradually increased, filling in between the solid particles, due to the role of the liquid phase surface tension, so that the unmelted particles further closer together, resulting in a sharp contraction of the volume, the decrease in the porosity, the density increases, such a Corresponding to the temperature at which the volume begins to change sharply is called the beginning of sintering temperature.
When the temperature continues to rise, the contraction will continue to increase to the maximum value, the porosity drops to the minimum value, the density reaches the maximum value, the viscous kuei completely sintered, the temperature corresponding to this time is called the sintering temperature.